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Density distributions, during the uniaxial cold compaction of an alumina powder, are obtained by both experimental and numerical studies. The density distributions of cylindrical specimens, compressed from one side, were measured with a special technique using X-ray imaging where fine lead balls were incorporated into the compacts. A constitutive model, based on the theory of non-linear elasticity,...

We study asperity fragmentation where two slabs of materials, each with a thickness of ∼ 100 , are moving parallel to each other at an ∼ 200 separation and at a relative velocity v varying from 1100 to110 the sound speed c 0 of the material. On opposite surfaces of the slabs protrude two wedges of height and base equal to ∼ 133 and collide along an infinite line length transverse...

With a view to determine the effect on the material properties of the interplay between oxygen ordering and the diffusive motion of metal-ion dopants in YBa 2 Cu 3-y M y O 6+x (M = Co, Fe, Al) we have developed, for a specific statistical mechanical model, a Monte Carlo computer-simulation algorithm in optimized C * and implemented the program...

Functional gradient materials (FGM) or materials with controlled anisotropy of concentration and properties, have been described by a micromechanical model. This model with the combination of micromechanics equations was used to calculate various mechanical (elastic moduli, Poisson's ratio) and thermal (thermal conductivity, diffusivity, specific heat) properties tensors' principal components. These...

In the framework of tight-binding approximation a new self-consistent method is presented for a quantitative description of both configurational and spectroscopic energies and related properties of solids with imperfections as well as large molecules. This method in respect of its capabilities is rather close to the semiempirical methods based on the neglecting differential overlap (NDO) approximation...

The configuration space of boron in silicon has been investigated using an empirical potential approach. This study indicates that energetically favourable configurations consist of a number of three-fold coordinated split interstitials. A configuration consisting of a four-fold boron-interstitial in combination with a two-fold silicon is found to be perfectly aligned in the 111 direction. ...

The Σ = 5 [001] twist boundary of Cu 3 Au is studied using the constant temperature, pressure and chemical potential difference Monte Carlo method. A N-body potential and bulk-like boundary conditions are utilized. The properties studied include the stoichiometry profile, the structure factor and the average position of the atoms along [001]. Various instantaneous atomic configurations are...

Using a mode-matching method, we investigate the ballistic transport properties of noninteracting electrons in two types of semiconductor nanostructures in which the confining potential has smooth, rounded corners. The rounded corners are simulated by dividing the structures into narrow strips and varying the width of each strip. The two structures we have investigated are a straight channel connecting...

The band structure of Ga 1-x Al x P under a uniaxial stress is calculated in the virtual crystal approximation (VCA) using the empirical pseudopotential method (EPM). We discuss the optical transitions in this system under a static uniaxial compression and a tension along a cubic direction [100], on the light of the change in energy caused by these stresses for states of...

A computational method to automatize some aspects of fracture analysis is presented. The method is based on the application of digital processing techniques to digitized bidimensional images of fractures, in order to obtain rugosity parameters based on fracture profiles. Also, the fractal dimension of the considered fractures are calculated, not in its classical form, as proposed by Mandelbrot,...

Viscoelastic materials can be represented by models consisting of springs and dashpots because the material shows elastic and viscous effects. The two simple models that are commonly used to relate stress and strain are the Maxwell (relaxation) and the Kelvin model (creep). These 2-parameter models are available in commercial FE-codes. The measured relation between stress and strain is generally...

Two mathematical techniques are presented: the method of point forces and the integral equation approach. They allow to compute stress intensity factors (SIFs) of cracks interacting with particles or fibers in composite materials. The interaction may result either from thermal and elastical mismatch between the heterogeneities and the surrounding matrix or from phase transformations associated with...

Under high temperature creep exposure, failure takes place due to the initiation and growth of intercrystalline cavities, in form of voids or intercrystalline creep micro-cracks.Statistical evaluation of the length of wedge type intercrystalline micro-cracks allows an estimation of their rate of growth as a function of the current value of crack length, grain size and creep conditions.An investigation...

Constitutive equations have been established to describe the behaviour of elastic-viscoplastic polymer materials initially exhibiting amorphous structure. Through the introduction of a state variable representation of back stress arising from network alignment, the constitutive equations model the large deformation behaviour of the material. A semi-automatic, computational technique has been developed...

The composite limit flow stress for transverse loading of metal matrix composites reinforced with continuous fibers is calculated using the finite element method. The focus of this work is to compare how different models for these composites influence the resulting composite flow behavior under transverse loading. Cell models with regular square and hexagonal arrangements [1] are compared with a...

The rolling and compression deformation textures of polycrystalline Ni 3 Al (L1 2 structure) and NiAl (B2 structure) aggregates are simulated by use of Taylor models. Various types of slip systems are considered, namely {111} <110> and {001} <110> for Ni 3 Al and {001} <100> and {011} <100> for NiAl. The activation of both types of slip in Ni 3...

Large strains in finite element simulations of metal forming require several remeshing procedures during the computation to take place. These remeshings should be performed automatically both for saving computational time and convenience. Such a remeshing algorithm has been well established for 2-dimensional applications and was recently presented for the 3-dimensional case.A special feature added...

Martensitic transformation is simulated in terms of computational micromechanics applying the finite-element method in order to study the effect of microstress and microstrain causing the unusual material behavior associated with stress-assisted martensitic transformation (MT). Both the preferred orientation of martensitic crystallographic variants (orientation effect) and microplastic deformation...

The increased demand for improved high-temperature materials in structural applications has driven researchers to examine a variety of light weight, high melting point alloys such as NiAl. This intermetallic compound has the desirable properties of high specific strength and oxidation resistance, although the strain to failure and toughness at room temperature are prohibitively low. Currently a...

The influence of inclusion arrangements and shapes on the mechanical and thermomechanical behavior predicted by unit cell descriptions of particle reinforced metal matrix composites is investigated. Three-dimensional cubic geometries, axisymmetric models and plane geometries are compared, and all periodic arrangements of inclusions are shown to display at least some degree of three-dimensional anisotropy...

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